Method for operating an electric vehicle

Abstract

Provided is an improved driving method for an electric vehicle equipped with a fuel cell system and a traction battery, which reduces the risk of speed suppression and optimizes energy utilization. 【Solution means】The present invention relates to a method for operating an electric vehicle (1) comprising a fuel cell system (2) and a traction battery (3). The method according to the present invention is characterized in that the target state of charge of the traction battery (3) is specified based on the terrain in the vicinity of the vehicle (1), for which purpose the position of the vehicle (1) is determined, the elevation is determined from a digital map in a predetermined surrounding area around the vehicle (1), and based on these, the probability of an uphill section and / or a downhill section occurring is estimated, and then the target state of charge is specified according to the probability of the uphill section and / or the downhill section.

Description

Technical Field

[0001] The present invention relates to a method for operating an electric vehicle comprising a fuel cell system and a traction battery.

Background Art

[0002] A typical problem in a hybrid vehicle comprising a primary drive unit and a traction battery, also called an HV battery or a high-voltage battery, is the distribution of power from the battery and other drive units. To optimally use the battery, it is assumed that it is possible to reliably estimate a section where the power requirement from the battery increases and a section where the amount of electric power secondarily generated by regeneration that needs to be stored in the battery increases.

[0003] In the case of a hybrid comprising an internal combustion engine and an additional storage battery, Patent Document 1 describes a control device that can adjust the charge state of the battery appropriately before going uphill or downhill based on a pre-planned route so as to optimize energy. The problem with the configuration described in that patent is that it only functions when traveling on a route planned using a navigation device. It is necessary to use a navigation system, that is, the user needs to actively input the destination of the route. Furthermore, it is assumed that the person driving the vehicle not only accurately follows this route but also does not deviate from the planned route. Such a deviation may require time-consuming recalculation, in which case the charge state of the battery cannot be optimally adjusted at the time of route change by the recalculation. When not using a navigation system, this method cannot be used either.

[0004] For further prior art, reference can be made to Patent Document 2. In that patent, a fuel cell vehicle, i.e., an electric drive vehicle equipped with a fuel cell, is described. When it is necessary to suppress due to the fuel cell reaching its maximum output, in order to prevent the vehicle speed from decreasing, the driving route can be optimized here, and as a result, it is possible to bypass relevant steep uphill slopes that may cause such an output limit according to the loading capacity of the trailer towed by the vehicle.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Here, the problem of the present invention is to provide an improved driving method that reduces the risk of speed suppression and optimizes energy utilization in an electric drive vehicle equipped with a fuel cell system and a traction battery.

Means for Solving the Problems

[0007] According to the present invention, this problem is solved by the method having the features of claim 1, in particular the features of the characterizing part of claim 1. Advantageous embodiments and developments are obtained from the dependent claims.

[0008] The method according to the invention contemplates that the target state of charge of the battery is specified based on the terrain surrounding the vehicle. For this purpose, for example, the position of the vehicle is determined via a satellite navigation system, and in a predetermined peripheral area around the vehicle, the elevation is determined from a digital map. Based on this elevation, the probability of the occurrence of an uphill section and / or a downhill section is determined, and then the target state of charge is specified according to the probability of the uphill section and / or the downhill section.

[0009] In contrast to the planned energy distribution of the main route entered into the navigation system, the method according to the invention can make useful estimates regardless of the use of the navigation system or whether the vehicle stays on this planned main route, and adapt the target state of charge accordingly. Thereby, the energy generated secondarily can be optimally stored, and the power required exceeding the maximum output of the fuel cell system can be utilized from the battery as needed. Thereby, on the one hand, the overall energy consumption is optimized, and on the other hand, for example, the risk of the speed being suppressed on the corresponding uphill slope is reduced.

[0010] In that case, according to a highly advantageous embodiment of the method according to the invention, it may be provided that when the probability of an uphill section is higher than that of a downhill section, a target state of charge exceeding 50-60% of the battery capacity is specified. According to a preferred development, the predefined value may be to exceed 80% of the battery capacity. Thereby, during regeneration, for example, the power generated secondarily during braking can be stored in the battery. However, based on the fact that the probability of an uphill section is higher than that of a downhill section, in this case, it may be premised that the vehicle is traveling in a relatively flat area and, for example, when passing a larger valley or the like, an uphill section may be predicted in some cases. That is, here, a larger amount of energy derived from regeneration should not be expected, so preferably a charge state of about 80% of the battery capacity, particularly a relatively higher charge state exceeding 80% of the battery capacity, is useful. Rather, it is necessary to anticipate that power from the traction battery will be required, and as a result, an uphill section that may occur, the probability of which is much higher than that of a downhill section, can be traveled with additional power from the traction battery, and output suppression is avoided.

[0011] According to an even more advantageous embodiment of the method according to the invention, when the probability of a downhill section is higher than that of an uphill section, a target state of charge of less than 50-60% of the battery capacity may be specified. According to an advantageous development of this embodiment, particularly less than 30% of the battery capacity may be specified. When the probability of a downhill section is higher than that of an uphill section, that is, when the vehicle is on a kind of plateau, for example, on a mesa, the probability of entering a downhill section going downward is clearly higher than the probability of overcoming an uphill section going upward from there. In this case, it may be premised with a relatively high probability that more regenerative power generated secondarily during braking will occur. In such a situation, since the state of charge of the battery is relatively low, less than 30%, all or at least most of this secondarily generated energy can be reliably stored and then reused for driving purposes.

[0012] According to a further embodiment of the method according to the invention, it is hereby also provided that, if the probability of the uphill section is approximately as high as the probability of the downhill section, the target state of charge is specified in the range of 50 to 60% of the battery capacity. That is, if the downhill section and the uphill section can be expected with similarly high probabilities based on the determined terrain, such an average state of charge of the traction battery can always be advantageous. This may correspond, for example, to the case in hilly or mountainous areas where the downhill and uphill sections usually appear alternately on the most appropriate route. In that case, the traction battery is maintained at a medium state of charge so that it can be actively assisted and stored, and in this case, both scenarios are predicted to occur with the same degree of probability.

[0013] A particularly advantageous embodiment of the method according to the invention may contemplate that the surrounding area in which the terrain is determined has a radius of about 50 km. That is, in the surrounding area around the vehicle, the terrain is preferably determined in the above-mentioned sense to provide for potential uphill and downhill sections occurring therein. In that case, according to an advantageous embodiment of the method according to the invention, this surrounding area can be specified at an angle of 360° around the vehicle, that is, as a result, the terrain in all directions from the vehicle is evaluated. Therefore, this is particularly useful when no navigation system is used and no other type of information regarding the potential travel destination is available at all.

[0014] However, advantageous embodiments of the method according to the invention can be used in the case of a route to a known destination without a route planned via a navigation system, or in the case of a route that has been frequently traveled in the past at a similar position of the vehicle. In this case, the angles of the surrounding area can be restricted to angular sections along the potentially predictable direction of travel. That is, here too, it is not limited to specific main routes, and the battery charge state is planned as accurately as possible along that main route to determine which provides ideal conditions. Rather, based on the general direction of travel, the surrounding area where the terrain is determined is correspondingly reduced. This reduction can be specified, for example, such that the angular section is reduced to 90 - 270° along the direction of travel according to other parameters. At 90°, it is considered a 45° arc on each of the right and left sides of this direction of travel as seen from the vehicle, and at 270°, this is correspondingly considered 135° each. This means, on the one hand, that less effort is required to evaluate the terrain, and on the other hand, it means that the large height differences in the area behind the direction of travel that would result in correspondingly steeper downhill or uphill sections can be ignored, and as a result, the quality of the evaluation is improved.

[0015] In that case, the angles can be restricted more severely in various ways depending on whether the direction of travel is based on the planned route of the navigation device, an estimate from the past, or a target position obtained from, for example, a calendar entry. If the route is specified relatively accurately by the navigation device, the angular section can be selected to be much smaller, i.e., in the range of 90 - 120°, and if the assumption of the preferred direction of travel based on past driving, etc., is relatively uncertain, the angular section can be selected to be larger accordingly, for example, 200 - 270°, to ensure a useful driving strategy.

[0016] Thus, overall, by optimizing the use of the traction battery, it is possible to reduce hydrogen consumption. Furthermore, this is particularly applicable to predictable uphill sections, and by optimizing the use of the traction battery, better vehicle performance, i.e., for example, preventing the suppression of vehicle speed, can be ensured. Additionally, the method according to the present invention, in one of the embodiments of the method described above, finally also enables more careful handling not only of the traction battery but also of the fuel cell system, and as a result, it is possible to achieve an improvement in service life through optimized use.

[0017] In that case, further advantageous embodiments of the method according to the present invention are also obtained from the exemplary embodiments shown in more detail below with reference to the drawings.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0019] In the illustration of FIG. 1, the vehicle 1 is shown very schematically, assuming that a fuel cell system 2 and a traction battery 3 are available. The vehicle is a commercial vehicle, here in the form of a truck, and consists of a tractor 4 and a trailer 5. However, other vehicles that can be designed as commercial vehicles or passenger cars, with or without a trailer, can be considered in the same way.

[0020] Vehicle 1 has a GPS sensor 6 in the area of the tractor 4, which is shown schematically in this figure. Through the GPS sensor 6, Vehicle 1 can determine its own position. The terrain of the area around Vehicle 1 can be determined at this time based on the position of Vehicle 1 determined through the GPS sensor 6 via a control unit inside the vehicle and / or a server (not shown) outside the vehicle, for example, the cloud. For this purpose, the elevation is read from a digital map stored in Vehicle 1 or a server outside the vehicle, and if there is no specific information regarding a potential driving route or direction of travel, it is evaluated in a predetermined peripheral area surrounding Vehicle 1, for example, within a 50 km radius. Depending on what elevation differences exist between the elevation of Vehicle 1 at the current position and the terrain it potentially travels on, uphill sections and / or downhill sections are determined, and as a result, in the finally specified peripheral area, on the one hand, the probability of an uphill section and, on the other hand, the probability of a downhill section can be determined. The target state of charge of the traction battery 3 is specified here based on these probabilities for the uphill and downhill sections.

[0021] This will be explained below using FIGS. 2 to 4 for three purely exemplary cases.

[0022] The example according to FIG. 2 shows here a vehicle 1 in a substantially flat area where there is higher terrain towards the ends. Accordingly, the potential uphill slope determined in the surrounding area is 838 m, while the downhill section is only 45 m. In this example, here merely by way of illustration, the area of Autobahn A5 between Karlsruhe and Basel is shown. In such an area, the probability of an uphill slope is relatively high, while the probability of a downhill slope is very low. That is, in this case, the target state of charge of the traction battery 3 is specified as a high value, for example, exceeding 80% of the battery capacity. This enables the ideal use of the traction battery 3. Since the downhill section need only be considered very limitedly, a fully charged battery can be used appropriately without the risk of not being able to store regenerative energy. At the same time, due to the high state of charge of the traction battery 3, it is possible to prepare for the electrical drive assistance of the vehicle 1 from the battery in the predicted uphill slope section where the probability is considerably higher.

[0023] The second embodiment according to FIG. 3 has the same logic as the illustration in FIG. 1 and shows the vehicle 1 driving on a plateau that is already at a higher level. As a result, the predicted cumulative elevation difference for the uphill section of approximately 380 m is added to the predicted cumulative elevation difference for the downhill section of approximately 1160 m, which is almost three times the value. In this case, the example of the terrain is taken from the federal road B500, the so-called "Schwarzwald-Hochstraße". In this situation, the probability of driving on the downhill section is very high, but the probability of driving on the uphill section can be evaluated as lower. That is, in this case, the target state of charge of the traction battery 3 can be specified to be relatively low, for example, about 30% of the battery capacity. In a similar scenario where the probability of the uphill section is even lower, it can be specified even lower. That is, in such a situation, it is necessary to assume that the probability of driving on the downhill section is relatively high. In that case, by using an electric drive machine with a wear-free brake, relatively more regenerative energy is generated incidentally during the operation of the generator. Since the target state of charge of the traction battery 3 is very low, the traction battery 3 can store all or at least most of this power generated incidentally during regeneration. As a result, energy-efficient driving occupies an important position.

[0024] The third example in FIG. 4 shows a vehicle in the area of a route in a mountainous or hilly area, and the scenario is taken from the autobahn A7 in the area of the "Kasseler Berge". In the relevant surrounding area, the terrain shows an uphill section with a cumulative elevation difference of approximately 800 m and a downhill section with approximately the same cumulative elevation difference. That is, in this case, it should be assumed that not only the downhill section but also the uphill section will be driven. In this case, the target state of charge of the traction battery 3 is specified in the intermediate range, for example, in the range of 50 - 60% of the battery capacity. Such an intermediate state of charge enables, on the one hand, assistance during driving on the uphill section and, on the other hand, enables storing at least most of the energy generated incidentally during regeneration on the downhill section, and then this energy can be reused on the next uphill section.

Claims

1. A method for operating an electric vehicle (1) comprising at least one fuel cell system (2) and at least one traction battery (3), wherein a target state of charge of the at least one traction battery (3) is specified based on the terrain in the vicinity of the vehicle (1), for which purpose the position of the vehicle (1) is determined, the elevation is determined from a digital map in a predetermined surrounding area around the vehicle (1), and based on these, the probability of an uphill section and / or a downhill section occurring is estimated, and the target state of charge is specified according to the probability of the uphill section and / or the downhill section, characterized in that it is a method.

2. The method according to claim 1, characterized in that when the probability of an uphill section is higher than that of a downhill section, the target state of charge is specified to exceed 50 - 60% of the battery capacity.

3. The method according to claim 2, characterized in that the target state of charge is specified to exceed 80% of the battery capacity.

4. The method according to claim 1, 2 or 3, characterized in that when the probability of a downhill section is higher than that of an uphill section, the target state of charge is specified to be less than 50 - 60% of the battery capacity.

5. The method according to claim 4, characterized in that the target state of charge is specified to be less than 30% of the battery capacity.

6. The method according to any one of claims 1 to 5, characterized in that when the probabilities of an uphill section and a downhill section are equally high, the target state of charge is specified in the range of about 50 - 60% of the battery capacity.

7. The method according to any one of claims 1 to 6, characterized in that the surrounding area is specified with a radius of about 50 km around the vehicle (1).

8. The method according to any one of claims 1 to 7, characterized in that the surrounding area is specified at an angle of 360° around the vehicle (1).

9. When there is no known driving route to a planned destination via a navigation system, or in the case of a driving route that has been frequently traveled in the past at the same position of the vehicle (1), the angle of the surrounding area is limited to an angular section along the predicted direction of travel, characterized in that it is the method according to any one of claims 1 to 7.

10. The method according to claim 9, characterized in that the limited angular section is specified in the range of 90 - 270°.

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